The nine families guarding Changsha are known as the "Old Nine Gates". Everyone knows their name. Among them, Zhang Qishan (played by William Chan), the head of the Nine Gates, was ordered to investigate the mystery of the ghost car and the mysterious mine. With his partner Qi Tiezui (played by Ying Haoming), they asked for help from Er Yuehong (played by Zhang Yixing), a famous opera actor born in an archaeological family. Unfortunately, Er Yuehong had already retired to take care of his seriously ill wife Yatou (played by Yuan Bingyan). In order to lead Er Yuehong out of the mountains again, Zhang Qishan and Qi Tiezui went north to the Crescent Hotel to seek medicine for Yatou. Afterwards, Zhang Qishan met Yin Xinyue (played by Zhao Liying), the eldest lady of the Crescent Hotel, and gradually developed feelings for each other. Although Yatou eventually died, Er Yuehong accidentally discovered that the mystery of the mine was closely related to his family predecessors, and it also concealed a shocking conspiracy planned by the Japanese.